At the height of its power in the 15th century, the Grand Duchy of Lithuania ruled over the territory of present-day Belarus, Latvia, Lithuania, and Ukraine, and parts of Estonia, Moldova, Poland, and Russia. In the Union of Lublin of 1569, the Grand Duchy and the Kingdom of Poland merged to form the Polish-Lithuanian Commonwealth. The commonwealth had a highly developed legal and administrative system, based on local land courts that decided civil cases involving the gentry and castle courts that dealt with other local matters, including criminal cases. Courts ...